Gas lubricated barrier seal

ABSTRACT

A double, back to back oriented mechanical end face seal (10) for use in sealing toxic or corrosive fluids having an intermediate buffer fluid chamber (26) into which a relatively inert gas, such as nitrogen, is provided for use as a buffer fluid. The nitrogen gas is maintained at a pressure which exceeds the process fluid pressure by at least 10 p.s.i. and, in a preferred embodiment, spiral pumping grooves (44,74) in the mating rings (40,60) of each of the seals (22,24) are shaped and dimensioned to pump the nitrogen buffer gas through the first seal (22) from the intermediate chamber (26) into the process fluid chamber (12) and through the second seal (24) from the intermediate chamber (26) into the environment external to the housing (12) and sealing area, thereby avoiding the escape of the process fluid into the intermediate buffer chamber (26) and to the atmosphere. Contamination of the process fluid by the buffer gas may be tolerated. The buffer gas may be any relatively inert gas, a gas which is non-hazardous to the environment and also is compatible with the process fluid used; appropriate examples are nitrogen, carbon dioxide, air or one of the noble gases. The seal (10) can be used to seal a process fluid which is either a liquid or a gas. &lt;IMAGE&gt;



